Heat exchanger and method of manufacturing same

ABSTRACT

Provided are a heat exchanger having a novel structure and efficiently cooling a heat generating body, and a method of manufacturing the heat exchanger. A heat exchanger has flow paths formed by being closed by an upper plate and a lower plate which have rectilinearly formed upstanding fins parallelly arranged at specific intervals, and gaps extend between adjacent fins in the top-bottom direction along the direction in which the fins extend. Either of or both the upper plate and the lower plate are provided with projections arranged in the longitudinal direction of the flow path and projecting inward of the flow path.

This is a national phase application filed under 35 U.S.C. 371 ofPCT/JP2009/062701 filed on Jul. 14, 2009, which claims the benefit ofpriority from the prior Japanese Patent Application No. 2008-190946filed on Jul. 24, 2008, the entire contents of all of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a heat exchanger provided with passagesdefined by a plurality of straight fins arranged in parallel, the heatexchanger being configured to allow a refrigerant or cooling medium topass through the passages to thereby dissipate heat from a heatingelement. Particularly, the invention relates to a heat exchanger inwhich passages for allowing a refrigerant to pass are formed to enhanceheat dissipation effect and a method of manufacturing the heatexchanger.

BACKGROUND OF THE INVENTION

Hybrid electric vehicles or the like incorporate a semiconductor devicein an inverter to drive a motor, and a water-cooling heat exchanger isadopted for cooling the semiconductor device. With respect to theinverter mounting the semiconductor device, higher output power has beendesired while a reduction in size and weight also has been demandedincreasingly. Accordingly, a demand for a heat exchanger excellent in aheat dissipation effect has been increased. Patent Literature Idescribed below discloses a conventional heat exchanger having improvedcooling performance. FIG. 16 is a sectional view of a heat exchanger ofPatent Literature 1 in a plan view.

A heat exchanger 100 includes a case 101 provided with a supply port 102and a discharge port 103. In the case 101, passages (flow paths) areformed to allow a refrigerant to pass from the supply port 102 to thedischarge port 103. In this heat exchanger 100, the passages are definedby a plurality of fins 111 and the passages are divided into three inthe linear direction; first, second, and third fin groups 201, 202, and203. Each of the fin groups 201 to 203 includes a plurality of the fins111 arranged in parallel with the lateral direction. The fins 111 ofeach fin group 201 to 203 are arranged in alignment with those of theadjacent fin groups to form a plurality of straight passages. Thestraight flow passages are however interrupted in between the fin groups201, 202, and 203 and merging sections 105 and 106 are formed there.

Further, the heat exchanger 100 is provided with separating fins 112placed between the laterally extending fins 111 to form a wide passage107 wider than the passages defined between the fins 111. In the thirdfin group 203, two adjacent separating fins 112 are connected to closeone end of the passage 107. Then, in this heat exchanger 100,semiconductor devices serving as heating elements are placedrespectively in nine sections partitioned by the merging sections 105and 106 and the separated passage 107 defined by the separating fins112. To be specific, in the heat exchanger 100, the refrigerant takeninto the exchanger 100 from the supply port 102 passes through thelinear passages formed between the fins 111. Multiple refrigerant flowsjoin together at the merging sections 105 and 106 to equalize flowdistribution and then diverge into downstream passages.

Patent Literature

Patent Literature 1: JP2007-335588A

SUMMARY OF INVENTION Technical Problem

When the passages defined by the fins are straight as in the heatexchanger 100, the refrigerant is apt to flow in laminar flow.Therefore, while the refrigerant flows fast in the central portion ofeach passage, the flow is slow in boundary layers or areas where therefrigerant contacts with the fins 111. As a result, the heat of eachheating element transferred to the fins is hard to be dissipated,interfering enhancement of the cooling performance. With regard to thispoint, an effective way to efficiently dissipate the heat from the finsby the refrigerant is to break the boundary layers by disturbing theflow of the refrigerant. However, traversing passages like the mergingsections 105 and 106 in the heat exchanger 100 are not enough to achievethe above effect.

In recent years, a semiconductor device tends to have larger heatgenerating density because of its reduced size. This leads to a demandfor improvement of the cooling performance of the heat exchanger to beused in an inverter or the like. In response to that, the heat exchangerin which the fins are arranged in an offset pattern has been proposed.However, the heat exchanger having such offset fin arrangement requirescomplicated working, leading to an increase in manufacturing cost.Especially, when the conventional fin member is formed by casting orother methods, a high processing cost is needed, which results in a highcost of the heat exchanger itself. Further, such fin member is hard tofinely machine and thus the improvement of cooling performance could notbe achieved.

The present invention has been made to solve the above problems and hasa purpose to provide a heat exchanger having a novel structure capableof efficiently cooling a heating element and a manufacturing method ofthe heat exchanger.

Solution to Problem

According to one aspect of the present invention, there is provided aheat exchanger having a plurality of upstanding fins formed linearly andarranged in parallel with each other at predetermined intervals, and anupper plate and a lower plate placed top and bottom in an upstandingdirection of the fins to enclose spaces between the adjacent fins toprovide a plurality of passages defined by the enclosed spaces, whereinat least one of the upper and lower plates includes a plurality ofprotrusions arranged in a longitudinal direction of each passage toprotrude therein, and the protrusions formed in the adjacent passagesare arranged in a staggered pattern in a direction perpendicular to aflat surface of the passages.

Further, in the above heat exchanger, it is preferable that the heatexchanger has: a fin member including the fins integrally formed on abase constituting either one of the upper and lower plates; and a coverplate constituting the other one of the upper and lower plates which isconnected to the fins in an opposite side from the base, wherein theprotrusions are formed on either the base or the cover plate.

In the above heat exchanger, preferably, the fin member is formed byextrusion-molding.

In the above heat exchanger, preferably, the protrusions are formed bypress working.

In the above heat exchanger, preferably, ones of the protrusionsadjacently arranged in a longitudinal direction of each passage areplaced at such intervals as to prevent cooling performance to begenerated between the protrusions from falling below a predeterminedreference value.

According to another aspect of the invention, there is provided a heatexchanger including a plurality of upstanding fins formed linearly andarranged in parallel with each other at predetermined intervals and anupper plate and a lower plate placed top and bottom in an upstandingdirection of the fins to enclose spaces between the adjacent fins toprovide a plurality of passages defined by the enclosed spaces, whereinone of the upper and lower plates includes a plurality of protrusionsprotruding into the passages in a longitudinal direction thereof; theheat exchanger includes: a fin member including the fins integrallyformed on a base constituting either one of the upper and lower plates;and a cover plate constituting the other one of the upper and lowerplates which is connected to the fins in an opposite side from the base,the protrusions being formed on either the base or the cover plate; thefin member is formed by extrusion-molding; the protrusions are formed bypress-fitting a punch in the base or the cover plate on an opposite sidefrom a passage surface to extrude a material toward the passage surfaceside; and when the protrusions are to be formed, a plate-shaped holdingmember is inserted in the spaces between the adjacent fins to hold thefins.

According to another aspect of the invention, there is provided a methodfor manufacturing a heat exchanger including a plurality of upstandingfins formed linearly in parallel with having predetermined spaces and anupper plate and a lower plate placed top and bottom in an upstandingdirection of the fins to enclose spaces between the adjacent fins,wherein one of the upper and lower plates includes a plurality ofprotrusions protruding into the passages in a longitudinal directionthereof; the heat exchanger includes: a fin member including the finsintegrally formed on a base constituting either one of the upper andlower plates; and a cover plate constituting the other one of the upperand lower plates which is connected to the fins in an opposite side fromthe base, the protrusions being formed on either the base or the coverplate; the fin member is formed by extrusion-molding; the fin member isformed as an intermediate fin member having raised portions eachcontinuous in the extruding direction in each space between the adjacentfins; and the protrusions are formed by inserting pressing platesseparately formed in the extruding direction into the spaces to squashthe raised portions except separating portions to form the protrusions.

Advantageous Effects of Invention

According to a heat exchanger of the invention, a refrigerant flowingthrough passages is disturbed its flow by protrusions so that boundarylayers contacting with fins are broken, and thereby the refrigerantderiving heat from the fins smoothly flows downstream without causingstagnation. Accordingly, the cooling performance is enhanced. Therefore,even when the heat generating density has been increased due to asmall-sized heating element, the heating element can be cooled comparedto the conventional one because the cooling performance has beenimproved. Further, the heat exchanger of the invention is simplyconfigured in a manner that passages defined by straight fins areprovided with protrusions, simplifying its structure and working andleading to cost reduction in manufacturing operation. In particular, theheat exchanger in the invention is manufactured by applying a fin memberformed by extrusion-molding and a base and a cover plate formed withprotrusions by pressing, so that mass production of the heat exchangeris achieved, capable of supplying the heat exchanger at low cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a heat exchanger according to anembodiment;

FIG. 2 is a perspective view of the heat exchanger from which a holdingframe is removed;

FIG. 3 is a perspective view of a fin member of the heat exchanger;

FIG. 4 is a diagram showing a flow of a refrigerant flowing inside apassage of the heat exchanger;

FIG. 5 is a graph showing a result of a cooling performance testconducted by flowing the refrigerant inside the passage of the heatexchanger;

FIG. 6. is a perspective view of the heat exchanger in use state;

FIG. 7 is a conceptual view showing one step of a working process toform the fin member for the heat exchanger;

FIG. 8 is a sectional view of a press device for forming protrusions;

FIG. 9 is a perspective view of a heat exchanger from which a holdingframe is removed in another embodiment;

FIG. 10 is a simplified diagram showing a working process of formingprotrusions in the fin member shown in FIG. 9;

FIG. 11 is a plan view showing one example of arrangement of theprotrusions in the passages;

FIG. 12 is a sectional view of a press device for forming protrusions;

FIG. 13 is a perspective view showing a method of forming theprotrusions by pressing;

FIG. 14 is a sectional view of the fin member immediately after theextrusion-molding before the protrusions are to be formed as shown inFIG. 13;

FIG. 15 is a perspective view of the fin member formed with theprotrusions formed by the method shown in FIG. 13; and

FIG. 16 is a planar sectional view of a conventional heat exchanger.

DETAILED DESCRIPTION OF EMBODIMENTS

A detailed description of a preferred embodiment of a heat exchanger anda method of manufacturing the same embodying the present invention willnow be given referring to the accompanying drawings. FIG. 1 is aperspective view showing a heat exchanger of the present embodiment.

A heat exchanger 1 includes a plurality of fins 11 arranged in a mainbody 2 formed in a rectangular tubular shape. The main body 2 has aninlet-side opening 21 and an outlet-side opening which open at both endsto form a plurality of passages 3. In the main body 2 of the heatexchanger 1, a refrigerant is allowed to flow in a direction indicatedby an arrow Q in the figure, thus the passages 3 extend through from theinlet-side opening 21 to the outlet-side opening.

In the heat exchanger 1 shown in FIG. 1, the inlet-side opening 21 andthe outlet-side opening largely open on either side of the main body 2.During use, on the other hand, the inlet-side opening 21 and theoutlet-side opening are closed and connected respectively to arefrigerant supply pipe or a refrigerant discharge pipe, both of whichare not shown. The refrigerant supply pipe is connected to a supply pumpfor pumping a refrigerant at a constant pressure to the heat exchanger 1and the refrigerant discharge pipe is connected to a tank for collectingthe refrigerant discharged from the heat exchanger 1.

The heat exchanger 1 includes a holding frame 13 having a U-shaped crosssection and an upper opening and a cover plate 14 fitted on thatopening, forming the tubular-shaped main body 2. A fin member 10 isincorporated in the main body 2 to form the plurality of passages 3.Herein, FIG. 2 is a perspective view of the heat exchanger 1 of FIG. 1from which the holding frame 13 is removed and FIG. 3 is a perspectiveview of the fin member 10 from which the cover plate 14 is removed.

The fin member 10 is integrally formed with the plurality of fins 11protruding from a base 12. The base 12 is a rectangular flat plate andformed with the fins 11 upstanding therefrom in a perpendiculardirection to the base 12. The fins 11 have the same height with eachother and the same length with the base 12 in a longitudinal direction.The adjacent fins 11 are arranged in parallel with one another. The thusconfigured fin member 10 is inserted in the holding frame 13 withoutbacklash and the cover plate 14 is placed on the holding frame 13 sothat the plate 14 abuts on tips of the fins 11. The heat exchanger 1 isintegrally configured by welding the fin member 10 mounted in theholding frame 13, the holding frame 13, and the cover plate 14.

In the heat exchanger 1, spaces between the adjacent fins 11 areenclosed by the base 12 as a lower plate and the cover plate 14 as anupper plate to define the passages 3 arranged in parallel. The fins 11at both end sides of the fin member 10 form spaces from the upstandingwall plates of the flame 13, the spaces being enclosed by the base 12and the cover plate 14 to form the passages 3.

When the refrigerant flows through the inlet-side opening 21 to the mainbody 2 in the direction Q in FIG. 1, the refrigerant branches off to thepassages 3 partitioned by the fins 11. In the heat exchanger 1 of thepresent embodiment, the passages 3 defined by the fins 11 are straightpaths and therefore the refrigerant tends to flow in laminar flow assame as the conventional technique, resulting in poor coolingperformance. Accordingly, the heat exchanger 1 of the embodiment isprovided with a configuration to disturb the refrigerant flow.Specifically, the cover plate 14 defining the passages 3 is formed withprotrusions 23 serving as obstacles to the refrigerant flowing throughthe passages 3.

The protrusions 23 are provided on an opposite side of recesses 25formed on one side of the cover plate 14 in the thickness direction asshown in FIG. 2, each protrusion 23 being spaced at a predeterminedinterval from each other in the vertical and lateral directions. To bemore concrete, the protrusions 23 are provided to be insertable in thespaces between the adjacent fins 11 so that the protrusions are presentat fixed intervals in each passage 3 when the cover plate 14 is set toassemble the heat exchanger 1 as shown in FIG. 1.

FIG. 4 is a diagram showing the flow of the refrigerant inside thepassage 3. Since the passage 3 defined by the fins 11 is linearlyformed, the flow of the refrigerant could be a laminar flow, leading tothe same problem with the conventional technique if the passage 3 isleft as it is. In the present embodiment, therefore, the flow of therefrigerant is disturbed by the existence of the protrusions 23 to breaka boundary layer contacting with the fins 11 generated in the laminarflow, thereby efficiently dissipating heat of the fins 11.

Further, especially in the heat exchanger 1 of the present embodiment,the protrusions 23 are placed at the specific intervals inside eachpassage 3 to maintain the cooling performance. FIG. 5 is a graph showinga result of a cooling performance test conducted by flowing therefrigerant in the passage 3. The horizontal axis of the graph indicatesspecific positions taken out from an arbitrary part of the passage 3 andthe vertical axis indicates the cooling performance (heat transfercoefficient). Passage points p1, p2, and p3 in the horizontal axisrepresent the positions in which the protrusions 23 are formed, and therefrigerant flows in the direction from the point p1 to the point p3.

The graph of FIG. 5 shows that the cooling performance of therefrigerant flowing through the passage 3 is not constant but changeslike a waveform. In other words, the heat transfer coefficient differsfrom position to position in the passage. Especially, in the graph k,the cooling performance goes up toward each of the points p1, p2, and p3representing the existence of the protrusions 23 and reaches at peakimmediately after each of the points p1, p2, and p3 and then the graphgradually goes down. This is because the flow of the refrigerant isdisturbed by the protrusions 23 and the refrigerant flows to efficientlyremove the heat from the fins 11. On the other hand, the graph goes downthereafter. This is conceivably because the flow of the refrigerantreturns to the laminar flow as it comes away from the protrusions 23, sothat the flow of the boundary layer contacting with the fins 11 tends tobe stagnant.

In response to this, in the present embodiment, the cooling performancerequired to dissipate heat of the heating element is set to be areference value “s” and the position of each protrusion 23 is determinedin a manner that the heat transfer coefficient would not fall below thereference value “s”. Specifically, the distance between the protrusions23 arranged in the longitudinal direction of the passage 3 is determinedso that the heat transfer coefficient indicated with the graph k goes upjust before the graph falls below the reference value “s”. The distancebetween the protrusions 23 differs depending on a size of the passage 3,a flow rate of the refrigerant to be supplied, the height of theprotrusions 23, a heat generating amount of the heating elements, andothers. Further, since the protrusions 23 also serve to interfere withthe flow of the refrigerant to cause pressure increase, the height ofeach protrusion 23 in the present embodiment is determined to be onethird of the passage 3, taking into account of the capability of thesupply pump and others.

In the heat exchanger 1 in use, as shown in FIG. 6 for example, a heatspreader 6 for thermal diffusion is placed on the cover plate 14 andsemiconductor devices 7 serving as heating elements are orderly arrangedon the heat spreader 6. When the semiconductor devices 7 used for aninverter or the like generate heat, the heat is transferred to the heatspreader 6 and diffused to be further transferred through the main body2 to the fins 11. In the main body 2, the refrigerant is supplied fromthe inlet-side opening 21 and flows toward the outlet-side opening inthe opposite side of the main body 2. As a result, the heat transferredto the fins 11 is taken away by the refrigerant flowing in contact withthe fins 11, so that heat dissipation is carried out.

The refrigerant flowing in each passage 3 is disturbed in flow by theprotrusions 23 to break the boundary layers contacting with the fins 11.Since the protrusions 23 are arranged with predetermined intervals, therefrigerant is caused to flow in each passage 3 while being constantlyagitated. Thus, the refrigerant having removed the heat efficientlyflows downstream. Especially, the cooling performance is maintainedequal to or higher than the reference value “s” in FIG. 5.

Even when the semiconductor devices are downsized, having a larger heatgenerating density, the heat exchanger 1 with extremely enhanced coolingperformance compared to the conventional ones can cool suchsemiconductor devices. Further, the heat exchanger 1 has such a simpleconfiguration of only providing the protrusions 23 in each passage 3defined by the fins 11 that less number of components are required,thereby enabling cost reduction.

The present embodiment realizes reducing the working cost formanufacturing the heat exchanger 1 having the excellent coolingperformance, and thereby providing the heat exchanger 1 at low cost. Themanufacturing method of such heat exchanger 1 is now explained.

First, the fin member 10 for the heat exchanger 1 is formed byextrusion-molding. A material used herein for the fin member 10 isaluminum having a good heat transfer coefficient. The molten material isextruded from a molding die for integrally forming the plurality of fins11 and the base 12, and a long-fin member having a several meters lengthis formed, for example. FIG. 7 is a conceptual view of a part of aworking process to form the fin member 10.

An extruded long-fin member 10L is directly transferred to and cut by apress device shown in the figure after the extrusion-molding. Thelong-fin member 10L is integrally formed with a long base 12L and longfins 11L vertically upstanding from the long base 12L. Thereafter, thelong-fin member 10L is transferred in the extruding direction F as shownin the figure. The long-fin member 10L just extruded remains softbecause a material forming the long-fin member 10L is heated to someextent. Such long-fin member 10L is further forwarded to and cut by apress device 50 for cutting.

The cutting press device 50 includes a not-shown lower die forsupporting a bottom part of the long base 12L and a plate-shaped upperdie 51 placed perpendicularly to the extrusion direction F to be movablevertically downward with respect to the lower die. The upper die 51 is aflat plate having a uniform thickness and a flat bottom end surface.Further, a pair of fin holding jigs 53 is provided on both sides of theupper die 51 to prevent the fins 11 from buckling and falling down dueto the pressing force of the upper die 51. Each of the fin holding jigs53 is formed with a plurality of flat plate-shaped supporting teeth 55to be inserted individually in the spaces between the adjacent fins 11.

The conveyance of the extruded long-fin member 10L is once. Then, thesupporting teeth 55 of the fin holding jigs 53 are individually insertedin the spaces between the adjacent long fins 11L of the long-fin member10L to support every single long fin 11L from both sides. Subsequently,the upper die 51 comes down to a space between the pair of fin holdingjigs 53 to cut off the long fins 11L at one time. At the same time, thelong base 12L is also cut off on the same cutting line with the longfins 11. In this cutting process, the long fin member 10L of long lengthis cut off at predetermined pitches, so that the plurality of finmembers 10 is successively produced. In addition, the holding frame 13is also formed by extrusion-molding and cutting as similar to the abovemethod.

A working or machining method for forming the cover plate 14 is nowexplained. The cover plate 14 is produced in such a way that a flatplate of a predetermined size is cut off from an aluminum plate having auniform thickness and formed with the protrusions 23 in predeterminedpositions. The protrusions 23 are formed in the flat plate by pressworking. FIG. 8 is a sectional view of a press device for formingprotrusions.

Each protrusion 23 of the heat exchanger 1 is of a triangular shape, butthe shape of the protrusion is not limited thereto as long as theprotrusion can perform the same function as the protrusion 23. ThoughFIG. 8 shows a press device for forming protrusions of cylindricalshape, the explanation of the pressing method is given regarding theprotrusions as same as the protrusions 23 in FIG. 2.

In a press device 60 for forming protrusions, a lower receiving base forholding a flat plate 14X is formed with a die 62. This die 62 is formedwith a die hole 61 of circular shape in cross section. On the otherside, an upper pressing base is provided with a stopper 63 for holdingdown the flat plate 14X by use of a not-shown spring and the stopper 63is formed with a guiding through hole 64 in which a tubular-shaped punch65 is inserted. A diameter of the punch 65 is designed to be wider thanthat of the die hole 61. FIG. 8 shows a partial configuration forforming one protrusion 23, but the press device 60 as a whole includes aplurality of identical configurations to that shown in FIG. 8 to form apredetermined number of protrusions 23 in the flat plate 14X at onetime.

In a protrusion forming process, the flat plate 14X is held in placebetween the die 62 and the stopper 63 and thereafter the punch 65 in theguiding through hole 64 is press-fitted in the flat plate 14X. At thattime, the punch 65 is press-fitted to the halfway of the flat plate 14Xwithout penetrating through the flat plate 14X. In the vicinity of thepress-fitted region of the flat plate 14X, a material of the surface ofthe flat plate 14X is drawn by the punch 65, but displacement of theflat plate 14X can be prevented by the stopper 63 to maintain the planarsurface to some extent. In the opposite side of the flat plate 14X fromthe punch 65, on the other hand, the material of the flat plate 14X isextruded into the die hole 61 to form a columnar shaped protrusion 23.With respect to the flat plate 14X, a predetermined number of theprotrusions 23 are formed by pressing. Thus the cover plate 14 is formedin one working operation.

According to the manufacturing method of the heat exchanger in thepresent embodiment, the fin member 10 is formed by cutting the long-finmember 10L by use of the press device 50 immediately after the long-finmember 10L is extrusion-molded. Therefore, a large number of the finmembers 10 can be produced in a short time compared to other methodssuch as casting. In particular, the material is cut immediately afterthe extrusion-molding while the material is still soft, so that there-heating process can be omitted, thus shortening the working time.Further, as for the cover plate 14, the protrusions 23 are formed bypress working of the flat plate 14X by use of the press device 60, sothat the working operation is simplified and working time is shortened,enabling mass production of the cover plate 14. This can reduce costsfor components of the heat exchanger 1 and hence provide the heatexchanger 1 itself at low cost.

An explanation is given for modifications of the above embodiment of theheat exchanger and the manufacturing method thereof.

In the heat exchanger 1 of the above embodiment, the protrusions 23 areformed in the cover plate 14. Alternately, protrusions 33 may be formedin a fin member 30 as shown in FIG. 9. FIG. 9 is a perspective view of aheat exchanger having the same configuration with the heat exchanger inFIG. 1 from which the holding frame 13 is removed. In this modification,a heat exchanger is configured such that the fin member 30 and a coverplate 34 are attached to the holding frame 13 shown in FIG. 1.

The fin member 30 is integrally formed with a plurality of fins 31perpendicularly formed on a base 32. The protrusions 33 are arranged inspaces between fins 31 arranged in parallel with each other atpredetermined intervals. The protrusions 33 shown in the figure areplaced in a passage formed in the space between one fin 31 and theholding frame 13. A plurality of the protrusions 33 are formed in eachpassage 3 in the longitudinal direction thereof at predeterminedintervals to maintain the cooling performance at the reference value “s”as shown in FIG. 5. On the other hand, the cover plate 34 in thismodification is a flat plate. However, the cover plate 34 may also beformed with protrusions to provide a heat exchanger having protrusionson both upper and lower sides of each passage 3. Further excellentcooling performance can be expected if the protrusions in each passage 3are displaced alternately, or staggered, between an upper side and alower side.

A method of manufacturing a heat exchanger, especially a step of workingor machining the fin member 30 having the protrusions 33 is nowexplained. FIG. 10 is a diagram showing a working step of forming theprotrusions 33 of the fin member 30 shown in a simplified manner. Thefin member 30 is formed as with the fin member 10 which is cut out fromthe long-fin member 10L as shown in FIG. 7. Thereafter, the fin member30 is further subjected to a pressing step for forming protrusions, inwhich the protrusions 33 are formed in the base 32.

A press device for forming a protrusion includes a pressing die 72 and areceiving die 74. The pressing die 72 includes a plurality of punches 71to be placed under the base 32 and the receiving die 74 is to receivepressing load. The receiving die 74 is formed with a plurality ofsupporting projections 73 arranged corresponding to the spaces betweenthe fins 31 so as to prevent the fins 31 from buckling and falling downdue to the load applied by the pressing die 72. Each fin 31 of the finmember 30 is inserted in each space between the supporting projections73 so that a tip of the fin 31 abuts on the receiving die 74 and isthereby supported. With respect to the supported fin member 30, thepunches 71 of the pressing die 72 are held against the base 32 and thematerial deformed by press-fitting of the punches 71 is extruded intothe spaces between the fins 31 to form the protrusions 33 in the base32.

In the heat exchanger 1 in FIG. 1, the protrusions 23 are arranged alongeach of the passages 3 (see FIG. 2) and further the protrusions 23 arearranged in rows in the direction perpendicular to the passages 3. Inthis case, if a distance between the adjacent fins 11 is set shorter inorder to enhance the cooling performance, a distance between theadjacent protrusions 23 could also be shorter. As a result, the adjacentpunches could interfere with each other because the punches for formingthe protrusions 23 are larger than the protrusions 23 in size. Further,the shorter distance between the adjacent protrusions 23 causesdeterioration of flatness of the cover plate 14. For instance, when theprotrusions 23 are to be formed in the cover plate 14 as shown in FIG.2, the material around each recess 25 is drawn by press-fitting of thepunches, generating some dents. Consequently, the dents around therecess 25 could be overlapped to enlarge deformation of the material ifthe distance between the adjacent recesses 25 is short.

In the case where the distance between the fins 11 is made shorter, theprotrusions 23 are arranged in a staggered pattern in the directionperpendicular to the fins 11, as shown in FIG. 11. Thereby, the distancebetween the adjacent protrusions 23 is increased and the interference ofthe punches can be avoided. It is thus possible to provide a heatexchanger with the fins 11 arranged at narrow distances from each otherto enhance the cooling performance. Furthermore, as well as theprotrusions 23, the distance between the adjacent recesses 25 is wider,so that deterioration of the flatness can be prevented. Incidentally, aninsulating sheet is bonded to a surface on which the recesses 25 are tobe formed, and the flatness therefor is assured.

Working for forming the protrusions provided in each passage is nowexplained. The press device for protrusions is disclosed in FIG. 8 forprocessing the protrusions, but alternately, an extrusion-molding typeof a press device shown in FIG. 12 may be adopted. A press device 80 forforming a protrusion includes a die 82 in a receiving base to be placedunder the flat plate 14X and the die 82 is formed with a recess 81conforming to the shape of the protrusion to be formed. In a pressingbase on the upper side, a stopper 83 for holding down the flat plate 14Xby use of a not-shown spring is provided. The stopper 83 is formed witha guiding through hole 84 penetrating through the stopper 83, and acolumnar-shaped punch 85 having an acute-angled tip is inserted in thehole 84.

The device of the present embodiment including the punch 85 smaller indiameter than the recess 81 is used to form the relatively largeprotrusions 23. On the contrary, the press device 60 in FIG. 8 issuitable for forming relatively small-sized protrusions. FIG. 12 showsonly a partial configuration of the press device 80 to from oneprotrusion 23, but the press device 80 is provided with a plurality ofidentical configurations to that shown in FIG. 12 to form apredetermined number of the protrusions 23 in the flat plate 14X at onetime. Even though the protrusion formed by the press device 80 in FIG.12 is of trapezoidal shape, which is different from the shape of theprotrusion in FIG. 2, it is also herein referred to as a protrusion 23.

In the press device 80, the flat plate 14X is held between andpositioned by the die 82 and the stopper 83. Thereafter, the punch 85 inthe guiding through hole 84 is press-fitted in the flat plate 14X. Thepunch 85 is pressed into the flat plate 14X until the tip of the punch85 reaches the recess 81. At this time, in the vicinity of the pressingregion, the surface material of the flat plate 14X is drawn by the punch85, but the stopper 83 restricts displacement of the plate and theflatness is maintained to some extent. On the opposite side of the flatplate 14X, the material is extruded into the recess 81, thereby formingthe trapezoidal-shaped protrusion 23. With respect to the flat plate14X, a predetermined number of the protrusions 23 are formed by thepress working, so that manufacturing of the cover plate 14 is completedin a single working.

The explanation is now given for a working method of forming extrusionsby pressing referring to FIG. 13. In the present modification, along-fin member is formed by extrusion-molding and then a fin member ofa predetermined length is cut off from the long-fin member. Further, theprotrusions are formed in the fin member by pressing as shown in FIG.13. A fin member 40 extrusion-molded in the present modification has asectional shape in the longitudinal direction as shown in FIG. 14.Specifically, fin members 41 are arranged perpendicularly protrudingfrom a base 42 at predetermined pitches and raised portion43 oftrapezoidal shape in section are formed between the fins 41 which definepassages. Each raised portion 43 is formed in continuous shape in thelongitudinal direction as same as the fins 41.

A press device 90 for forming protrusions includes a lower die 91 forsupporting the fin member 40 from the bottom side and an upper die 92for shaping protrusions. The upper die 92 includes pressing plates 95,96, and 97 each inserted in a clearance 45 between the fins 41. One setof the pressing plates 95, 96, and 97 are placed linearly along theclearance 45 and formed with separating portions 98 in between theplates. A plurality of sets of the pressing plates 95, 96, and 97 areplaced to hold each fin 41 from both sides, the sets of plates beingarranged in parallel to one another as shown in the figure. In thefigure, each pressing plate 95, 96, and 97 is shown in an independent(separated) state, but the plates are configured to integrally transmita pressing load applied by a single pressurizing device.

The press device 90 is configured to move the upper die 92 downward tothe fin member 40 having the sectional view in FIG. 14 so that thepressing plates 95, 69, and 97 are inserted in the clearances 45 to holdthe fins 41. The upper die 92 continues to move down to squeeze orsquash the raised portion 43 pressurized by the plates 95, 96, and 97.At this time, the portions of the fins 41 located in the separatingportions 98 between the plates 95, 96, and 97 are not squashed, so thatprotrusions 46 are formed as shown in FIG. 15.

Therefore, according to the manufacturing method of the presentembodiment, the protrusions 46 can be formed by use of a simple diewithout requiring a processing device having a complicated die forforming protrusions. Accordingly, a cost for a processing device can bereduced, leading to cost reduction in processing a heat exchanger.

While the presently preferred embodiment of the heat exchanger and themanufacturing method thereof according to the present invention has beenshown and described, the invention is not limited to the aboveembodiments and may be embodied in other specific forms withoutdeparting from the essential characteristics thereof.

REFERENCE SIGNS LIST

1 Heat exchanger

2 Main body

3 Passage

6 Heat spreader

7 Semiconductor device

10 Fin member

11 Fin

12 Base

13 Holding frame

14 Cover plate

23 Protrusion

50 Press device for cutting

60 Press device for forming protrusions

62 Die

63 Stopper

65 Punch

1. A heat exchanger having a plurality of upstanding fins formedlinearly and arranged in parallel with each other at predeterminedintervals, and an upper plate and a lower plate placed top and bottom inan upstanding direction of the fins to enclose spaces between theadjacent fins to provide a plurality of passages defined by the enclosedspaces, wherein at least one of the upper and lower plates includes aplurality of protrusions arranged in a longitudinal direction of eachpassage to protrude therein, and the protrusions formed in the adjacentpassages are arranged in a staggered pattern in a directionperpendicular to a flat surface of the passages.
 2. The heat exchangeraccording to claim 1 having: a fin member including the fins integrallyformed on a base constituting either one of the upper and lower plates;and a cover plate constituting the other one of the upper and lowerplates which is connected to the fins in an opposite side from the base,wherein the protrusions are formed on either the base or the coverplate.
 3. The heat exchanger according to claim 2, wherein the finmember is formed by extrusion-molding.
 4. The heat exchanger accordingto claim 3, wherein the protrusions are formed by press working.
 5. Theheat exchanger according to claim 1, wherein ones of the protrusionsadjacently arranged in a longitudinal direction of each passage areplaced at such intervals as to prevent cooling performance to begenerated between the protrusions from falling below a predeterminedreference value.
 6. A heat exchanger including a plurality of upstandingfins formed linearly and arranged in parallel with each other atpredetermined intervals and an upper plate and a lower plate placed topand bottom in an upstanding direction of the fins to enclose spacesbetween the adjacent finds to provide a plurality of passages defined bythe enclosed spaces, wherein one of the upper and lower plates includesa plurality of protrusions protruding into the passages in alongitudinal direction thereof; the heat exchanger includes: a finmember including the fins integrally formed on a base constitutingeither one of the upper and lower plates; and a cover plate constitutingthe other one of the upper and lower plates which is connected to thefins in an opposite side from the base, the protrusions being formed oneither the base or the cover plate; the fin member is formed byextrusion-molding; the protrusions are formed by press-fitting a punchin the base or the cover plate on an opposite side from a passagesurface to extrude a material toward the passage surface side; and whenthe protrusions are to be formed, a plate-shaped holding member isinserted in the spaces between the adjacent fins to hold the fins.
 7. Aheat exchanger including a plurality of passages defined by a pluralityof upstanding fins formed linearly in parallel having predeterminedspaces and an upper plate and a lower plate placed top and bottom in anupstanding direction of the fins to enclose the spaces between theadjacent fins, wherein one of the upper and lower plates includes aplurality of protrusions protruding into the passages in a longitudinaldirection thereof; the heat exchanger includes: a fin member includingthe fins integrally formed on a base constituting either one of theupper and lower plates; and a cover plate constituting the other one ofthe upper and lower plates which is connected to the fins in an oppositeside from the base, the protrusions being formed on either the base orthe cover plate; the fin member is formed by extrusion-molding, the finmember is formed as an intermediate fin member having raised portionseach continuous in the extruding direction in each space between theadjacent finds; and the protrusion are formed by inserting pressingplates separately formed in the extruding direction into the spaces tosquash the raised portions except separating portions to form theprotrusions. 8-10. (canceled)